|Trimbos Institute: Netherlands Institute of Mental Health and
PO Box 725
3500 AS Utrecht
Tel.: (030) 279 11 00
|Dr. R.J.M. Niesink.
|Goal of the study:
||To investigate the concentration of delta-9-tetrahydrocannabinol
(THC) in marihuana and hash as sold in Dutch coffeeshops. In addition it is
studied whether there are differences between the cannabis products originating
from Dutch grown hemp (nederwiet) and those derived from foreign hemp.
|Type of study:
- What are the THC concentrations in marihuana and hash?
- Are there differences in these concentrations between Dutch and foreign grown maruhuana
- Is there a relation between THC concentration and price of the marihuana products?
- Are the concentrations different from those found in other countries?
- Is there an increase or decrease of the THC-concentration over a certain time-period?
|Coffeeshops in The Netherlands.
|Every year, 50 coffeeshops are randomly selected. For the purpose
of the study, samples of nederwiet, foreign marihuana, Dutch hash and foreign
hash are anonymously bought in the selected coffeeshops. After the transaction a
number of questions about the samples are asked to the shop keeper. THC
concentrations are chemically analysed in a specialized laboratory.
||The Ministry of Health, Welfare and Sport (VWS)
PO Box 800
3170 DZ Poortugaal
||The Ministry of Health, Welfare and Sport (VWS) and the Ministry of
||The average THC content of the marihuana samples in 1999 was 7.5%
and that of the hash-samples 12.6%. The average THC content of nederwiet (8.6%)
was significantly higher than that of foreign marihuana (5.0%). Hash derived
from Dutch hemp contained more THC (20.7%) than hash originating from foreign
hemp (11.0%). These THC percentages do not deviate much from the percentages
that have been reported by the Dutch Forensic Institute in the middle of the
nineties about confiscated marihuana and hash samples. The prices that had to be
paid for nederwiet and Dutch hash were higher than the prices for foreign
marihuana and hash. The price for nederwiet in Amsterdam was higher than in the
rest of the country. There is a significant correlation between price and THC
content of the cannabis products.
When the THC concentrations in nederwiet are compared with the THC
concentrations in marihuana from foreign studies it must be concluded that the
concentrations in nederwiet are nothing out of the way. The THC-content of
nederwiet is comparable with the THC content of sinsemilla samples as measured
in the US between 1980 and 1997.
Niesink, R.J.M. (2000) THC-concentraties in wiet, nederwiet
en hasj in Nederlandse coffeeshops. Utrecht, Trimbos-institute.
||Project is part of the program Epidemiology and Monitoring of
Addiction of the Trimbos institute.